Technical Field
The present disclosure relates to an integrated data concentrator for multi-sensor MEMS systems, in particular provided with the so-called “pass-through” operating mode.
Description of the Related Art
The increasing use of sensors including micromechanical structures made, at least in part, of semiconductor materials and with MEMS (Micro-Electro-Mechanical Systems) technology is known in portable electronic apparatuses, such as, for example, laptops, tablets, smartphones, digital audio players, photographic cameras or video cameras, and consoles for videogames.
These sensors have advantageous characteristics, amongst which extremely compact dimensions, reduced consumption levels, and good electrical performance, and may be used for example for inertial-navigation applications, for providing user interfaces, for detecting displacements in three-dimensional space, or for detecting environmental parameters (such as pressure, humidity, temperature).
In particular, so-called “multi-sensor systems” have recently been proposed, which envisage joint and combined use of a wide range of sensors, for example accelerometers, gyroscopes, pressure sensors, humidity sensors, temperature sensors, magnetometers. These sensors may be provided within one and the same package, in an integrated manner; alternatively, the various sensors may be physically distinct, but in any case functionally connected, for example via a communication bus.
The above multi-sensor systems enable grouping, within a single integrated system, of a plurality of detection possibilities, which may advantageously concur in providing one or more common functions, for example for providing an accurate motion-detection system.
In order to facilitate management by an external microprocessor (typically the microprocessor of the host portable electronic apparatus), the multi-sensor system comprises an integrated data concentrator (the so-called “sensor hub”, this term being used hereinafter), having, amongst other functions, the function of interfacing between the integrated sensors and the external microprocessor.
For instance, the sensor hub, typically including a microcontroller (or a similar processing unit, for example a “picocontroller”, or implemented by means of FPGA—Field-Programmable Logic Array), acquires detection signals read by the various sensors, which are typically connected to a single digital communication bus, and supplies these signals to the external microprocessor, possibly after suitable processing operations.
Generally, the presence of a sensor hub relieves the external microprocessor from the task of monitoring the outputs of the plurality of sensors, providing a single acquisition interface, and moreover from the computational burden linked to at least part of the signal-processing operations.
FIG. 1 is a schematic representation of a sensor hub 1, which implements: a first interface module 2a, for connection to an external microprocessor 3, through a first digital communication bus 4, of a bidirectional type; and a second interface module 2b, for connection to a plurality of sensors 6, through a second digital communication bus 8, of a bidirectional type.
Typically, in a “standard” or “normal” operating mode, the first interface module 2a operates in “slave” mode with respect to the external microprocessor 3 in the communication through the first digital communication bus 4 (main bus), which may for example be regulated by a serial protocol, such as the I2C protocol (Inter Integrated Circuit) or SPI (Serial Parallel Interface), and the second interface module 2b operates in “master” mode with respect to the sensors 6 in the communication through the second digital communication bus 8 (auxiliary bus), which may, for example, be regulated by the same serial protocol or else by a different one.
A specific operating mode that is generally used by a sensor hub is the one referred to as “pass-through” mode, which envisages providing a direct communication path between the external microprocessor and the various sensors coupled to the communication bus, in particular operating conditions, in effect rendering the sensor hub itself “transparent” for the external microprocessor.
Generally, it is moreover desired to allow a complete freedom of choice by the system on the use, or otherwise so, of the sensor hub during acquisition of the signals.
For instance, the pass-through operating mode may prove advantageous in a step of configuration of the sensors in order to allow the external microprocessor to set directly configuration parameters for the same sensors, thus preventing a double operation of configuration, first of the sensor hub by the external microprocessor, and then of the sensors by the sensor hub.
As a further example, the pass-through operating mode may prove advantageous in the case where some sensors coupled to the communication bus are inactive, the interface operation provided by the sensor hub being in fact convenient when a sufficiently high number of sensors is present.
A solution of a known type for providing the aforesaid pass-through mode envisages, as shown schematically in FIG. 2, the use of appropriate analog switch elements, designated by 9, which are suitably controlled by an electrical control signal Sa received at input from the sensor hub 1 in order to create a direct electrical-connection path between the sensors 6 and the external microprocessor 3. The analog switches 9 hence provide a sort of short circuit between the first and second digital communication buses 4, 8.
The analog switches 9 are electrically connected between input and output pads (not shown in the figure) of the sensor hub 1, as additional analog discrete components.
Consequently, such an implementation of the pass-through mode uses a modification at the physical, circuit level of the sensor hub, and uses a knowledge of the construction of the electrical-interconnection paths and of the configuration of the pads of the sensor hub. Furthermore, the presence of the analog switches entails an evident increase in terms of area occupation.